U.S. patent application number 14/901919 was filed with the patent office on 2016-10-27 for electrically heated filter screens.
The applicant listed for this patent is UNITED TECHNOLOGIES CORPORATION. Invention is credited to Taylor FAUSETT, Patrick M. WASSON.
Application Number | 20160311552 14/901919 |
Document ID | / |
Family ID | 52144112 |
Filed Date | 2016-10-27 |
United States Patent
Application |
20160311552 |
Kind Code |
A1 |
FAUSETT; Taylor ; et
al. |
October 27, 2016 |
ELECTRICALLY HEATED FILTER SCREENS
Abstract
A heating body for an electrically heated filter screen includes
a heater element having an outer surface and a metallic protective
layer having an inner surface. An insulating layer is disposed
between the heater element outer surface and the inner surface of
the metallic layer. The metallic layer and an exposed portion of
the insulating layer define an exterior of the heating body. An
electrically heated filter screen constructed from pairs of
intersecting heating bodies is also described.
Inventors: |
FAUSETT; Taylor; (San Diego,
CA) ; WASSON; Patrick M.; (El Cajon, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
UNITED TECHNOLOGIES CORPORATION |
Hartfotd |
CT |
US |
|
|
Family ID: |
52144112 |
Appl. No.: |
14/901919 |
Filed: |
June 6, 2014 |
PCT Filed: |
June 6, 2014 |
PCT NO: |
PCT/US2014/041262 |
371 Date: |
December 29, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61842575 |
Jul 3, 2013 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F02C 7/224 20130101;
B01D 35/005 20130101; H05B 2203/024 20130101; B64D 37/32 20130101;
H05B 3/16 20130101; B01D 35/18 20130101; B64D 37/34 20130101 |
International
Class: |
B64D 37/32 20060101
B64D037/32; B01D 35/18 20060101 B01D035/18; H05B 3/16 20060101
H05B003/16; B01D 35/00 20060101 B01D035/00; B64D 37/34 20060101
B64D037/34; F02C 7/224 20060101 F02C007/224 |
Claims
1. A heating body for an electrically heated filter screen,
comprising: a heater element with a surface; a metallic layer with
an inner surface; and an insulating layer disposed between the
heater element surface and the metallic layer inner surface for
electrically insulating the heater element from fuel contacting the
metallic and insulating layers of the heating body.
2. A heating body as recited in claim 1, wherein a portion of the
insulating layer defines an exposed exterior surface portion of the
heating body.
3. A heating body as recited in claim 1, wherein the metallic layer
defines an exterior surface portion of the heating body opposite
the insulating layer exterior surface portion.
4. A heating body as recited in claim 1, wherein the insulating
layer has an annular cross-sectional area disposed about the heater
element.
5. A heating body as recited in claim 1, wherein the metallic layer
defines an upstream face of the heating body.
6. A heating body as recited in claim 1, wherein the metallic layer
is in direct physical contact with the insulating layer.
7. A heating body as recited in claim 1, wherein a cross-section of
the heating body defines lateral and an axial widths, the lateral
width being orthogonal with respect to the axial width.
8. A heating body as recited in claim 7, wherein the lateral width
of the heating body is greater than the axial width of the heating
body.
9. A heating body as recited in claim 7, wherein the axial width of
the heating body is greater than the lateral width of the heating
body.
10. A heating body as recited in claim 7, wherein a thickness of
the metallic layer is greater along the lateral width than along
respective thicknesses along the lateral width.
11. A heating body as defined in claim 1, wherein the insulating
layer circumferentially surrounds the surface of the heating
element, and wherein the surface of the metallic layer and surface
portion of the insulating layer collectively define an exterior of
the heating body.
12. A heating body as defined in claim 1, wherein the insulating
layer electrically insulates the heater element from the
environment external to the heating body.
13. A heating body as defined in claim 1, wherein the heater
element is thermally communicative with the environment external to
the heating body through the metallic layer.
14. An electrically heated filter screen for a fuel system,
comprising: a first heating body pair as recited in claim 1 and
extending in a first orientation; a second heating body pair as
recited in claim 1 and extending in a second orientation, wherein
the second heating body pair is coupled to the first heating body
pair; and an aperture defined by the first heating body pair and
the second heating body pair and extending through the electrically
heating filter screen from the metallic layer to an exposed portion
of the insulating layer.
15. An electrically heated filter screen as recited in claim 14,
wherein the metallic layers of the first heating body pair and the
second heating body pair face in a common direction and define an
upstream face of the electrically heated filter screen.
16. An electrically heated filter screen as recited in claim 14,
wherein exposed portions of the insulating layers of the first
heating body pair and the second heating body pair define a
downstream face of the electrically heated filter screen.
17. An electrically heated filter screen as recited in claim 14,
wherein each heating body of the first heating body pair is
parallel with the other.
18. An electrically heated filter screen as recited in claim 17,
wherein the second heating body pair is orthogonal with respect to
the first heating body pair.
19. An electrically heated filter screen as recited in claim 14,
wherein the screen is disposed in a union coupling upstream
adjacent downstream fuel conduits.
20. An electrically heated filter screen as recited in claim 14,
wherein the metallic layer faces into a fuel flow and is configured
and adapted to block and melt ice particles entrained in a fuel
flow traversing the electrically heated filter screen.
Description
RELATED APPLICATIONS
[0001] This application claims the benefit of and priority to U.S.
Provisional Patent Application No. 61/842,575 filed Jul. 3, 2013,
the contents of which are incorporated herein by reference in their
entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present disclosure relates to electrically heated filter
screens, and more particularly to electrically heated filter
screens with metal protective layers for aircraft fuel systems.
[0004] 2. Description of Related Art
[0005] Gas turbine engine fuel systems operate in wide range of
environmental conditions. In extremely cold operating environments
such fuel systems are susceptible to ice formation in fuel tanks,
conduits, valves, and other system components. Ice formation can
occur when either fuel or water contaminating the fuel is exposed
to low temperature for extended time periods.
[0006] To combat icing, electrically heated filter screens can be
provided within the fuel system. Electrically heated filter screens
operate to capture and melt ice conveyed through the fuel system
prior to it becoming lodged in the system and affecting engine
operation. Conventional electrically heated filter screens may
include a heater element coated with a ceramic layer. The ceramic
layer functions to electrically insulate the heater element from
fuel flowing through the screen and to provide efficient thermal
conductivity between the heater element and fuel traversing the
electrically heated filter screen.
[0007] Conventional electrically heated filter screens have
generally been considered satisfactory for their intended purpose.
However, there is a need for electrically heated filter screens
resistant to damage from ice, contamination and debris entrained in
fuel as it flows through the fuel system. There also remains a need
for electrically heated filter screens that are easy to make and
use. The present disclosure provides a solution for these
problems.
SUMMARY OF THE INVENTION
[0008] The subject disclosure is directed to a new and useful
heating body for an electrically heated filter screen (EHFS). The
heating body includes a heater element, a metallic layer, and an
insulating layer disposed between a surface of the heater element
and an inner surface of the metallic layer. The insulating layer
electrically insulates the heater element from the environment
external to the heating body. The metallic layer and an exposed
portion of the insulating surface define an exterior surface of the
heating body, the metallic layer further defining an exterior
surface portion opposite the exposed surface portion of the
insulating layer.
[0009] In embodiments, the insulating layer defines an annular
cross-sectional shape disposed about a circumference of the heater
element. It is contemplated that the metallic layer form an
upstream face of the heating body and that the exposed surface
portion of the insulating layer face form a downstream face of the
heating body.
[0010] The metallic layer can be in direct physical contact with
the insulating layer, and the insulating layer can be in direct
physical contact with the heater element. It is contemplated that
the heater element is thermally communicative with environment
external to the heating body through the insulating layer and
metallic layer.
[0011] A cross-sectional area of the heating body defines lateral
and axial widths substantially orthogonal with respect to one
another. In embodiments, the lateral width is greater than the
axial width. In embodiments, the axial width of the heating body is
greater than its lateral width.
[0012] An EHFS is also provided. The EHFS includes a first heating
body pair and a second heating body pair arranged at angle to, and
coupled with, the first heating body pair. An aperture is defined
through the EHFS between intersections of the first heating body
pair and the second heating body pair. It is contemplated that
metallic layers of the heating bodies face of the first and second
heating body pairs face a common direction to form an upstream face
of the EHFS. Opposite exposed surface portions of the insulating
layers of the first and second heating body pairs form a downstream
face of the EHFS. In embodiments, each heating body of the first
heating body pair is parallel with respect to the other. In certain
embodiments, the second heating body pair is orthogonal with
respect to the first heating body pair.
[0013] The EHFS can be captive in a union fluidly coupling adjacent
upstream and downstream fuel conduits. It is contemplated that the
metallic layer of the heating bodies face upstream, into fuel
flowing from the upstream conduit and into the downstream conduit,
and that the EHFS be configured and adapted to melt ice entrained
in the fuel flow as well as protect the insulating layer and
heating element from impact of ice particles entrained in the fuel
flow.
[0014] In accordance with certain other embodiments, these and
other features of the systems and methods of the subject disclosure
will become more readily apparent to those skilled in the art from
the following detailed description of the preferred embodiments
taken in conjunction with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Preferred embodiments thereof will be described in detail
herein below with reference to certain figures, wherein:
[0016] FIG. 1 is a schematic view of a fuel system for a gas
turbine engine, according to an embodiment;
[0017] FIG. 2 is a cross-sectional schematic view of a portion of
the fuel system of FIG. 1 showing an electrically heated filter
screen (EHFS), according to an embodiment;
[0018] FIG. 3 is a plan view showing a face of the EHFS of FIG. 2,
according to an exemplary embodiment;
[0019] FIG. 4 is a cross-sectional view of the EHFS of FIG. 2
showing profiles of heating bodies of the EHFS of FIG. 2;
[0020] FIG. 5 is a cross-sectional view of one of the heating body
profiles of FIG. 4 showing the layers thereof, according to an
embodiment; and
[0021] FIG. 6 is a cross-sectional view of another heating body
profile having an elongated profile, according to another exemplary
embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0022] Reference will now be made to the drawings wherein like
reference numerals identify similar structural features or aspects
of the subject disclosure. For purposes of explanation and
illustration, and not limitation, a partial view of an exemplary
embodiment of an electrically heated filter screen (EHFS) in
accordance with the disclosure is shown in FIG. 1 and is designated
generally by reference character 100. Other embodiments in
accordance with the disclosure, or aspects thereof, are provided in
other figures, as will be described. The system of the disclosure
can be used for gas turbines such as aircraft main and auxiliary
power unit (APU) engines. As will be appreciated embodiments of the
EHFS disclosed herein are also suitable for use in marine or
terrestrial gas turbines.
[0023] With reference to FIG. 1, a fuel system 10 for an aircraft
is shown. Fuel system 10 includes a fuel tank 12 fluidly coupled to
a turbojet fuel system 14 by a conduit 16, a union 20, and a
conduit 18. Conduit 16 is arranged upstream of union 20 and fluidly
couples fuel tank 12 to union 20. Conduit 18 is arranged downstream
and fluidly couples union 20 to turbojet fuel system 14. Turbojet
fuel system 14 includes a heat exchanger 22 coupled to a fuel
module 26 by a conduit 24, a fuel manifold 30 coupled by a conduit
28 to fuel module 26, and a combustor 34 coupled to fuel manifold
30 by a conduit 32. As will be appreciated, fuel module 26 can
include additional elements such fuel pumps, fuel solenoids, and
fuel filters (not shown), and can be for either an aircraft main
engine or APU. As will also be appreciated, other fuel system
configurations having other components are possible and are within
the scope of the present disclosure.
[0024] Union 20 includes EHFS 100. EHFS 100 is arranged in union 20
such that fuel flowing from upstream of union 20 traverses EHFS
100. Electrical leads 38 and 40 electrically connect EHFS 100 to
turbojet or aircraft electronics 36. Aircraft electronics 36 can
include a power source, such as a DC or AC power supply for
example. In an embodiment, EHFS 100 is operatively coupled to a DC
power bus of an aircraft through aircraft electronics 36.
[0025] Fuel flows from fuel tank 12 to turbojet fuel system 14
through a fluid channel defined by conduit 16, union 20, and
conduit 18. Fuel arriving at EHFS 100 can be unheated and/or be not
filtered to an appropriate level for turbojet fuel system 14. It
can also include entrained ice particles. Ice can form within
aircraft fuel system 10 from exposure to cold temperatures during
flight, and thereafter be mobilized into the fuel flow by system
component warming, vibration, or changes in fuel flow rate. Icing
can present operation challenges to main engines, such as loss of
power due to fuel starvation. Icing can be particularly problematic
for APUs which can rest during flight in icing conditions with
little or no fuel flow, accumulating ice, and thereafter be
activated while in freezing conditions. Portions of aircraft fuel
systems leading to APUs are particularly prone to icing due to the
tendency of fuel to linger in the system while the APU is idle,
such as when the APU is off for an extended period during flight at
altitude and exposed to below freezing temperatures.
[0026] Once entrained in fuel flow, ice particles can impact and
damage internal fuel system components and structures. Ceramic
coated EHFS are particularly susceptible to ice damage because
ceramic coatings are relatively brittle and chip easily. Ceramics
are rendered more vulnerable to impact damage by cold ambient
temperatures, such as can be experienced during aircraft flight at
extreme altitude. Moreover, operation an EHFS in a mode where it is
cycle don and off induces thermal stress due to mismatches between
the coefficients of expansion of the heater element and ceramic
coating--such as in fuel systems that cycle an EHFS on and off
during operation to limit power consumption for example.
[0027] With reference to FIG. 2, a portion of fuel system 10 is
shown including conduit 16, conduit 18, and union 20. EHFS 100 is
illustrated in union 20 rotated relative to an axis extending
vertically through EHFS 100 to show an upstream face 101 of EHFS
100. As will be appreciated, EHFS 100 also defines a corresponding
downstream face (not shown) on its opposite side. EHFS 100 is
configured and adapted to screen downstream engine components, such
as filters, heaters, pumps and the like from ice particles
entrained in fuel flowing from upstream of conduit 16 in the
downstream direction and into conduit 18. EHFS 100 is also
configured and adapted to melt screened ice that becomes captive on
upstream face 101 of EHFS 100 by fuel flowing through EHFS 100.
Positioning EHFS 100 in union 20 makes the EHFS accessible for
servicing, inspection, cleaning, or replacement. As will be
appreciated, one or more EHFS 100 can be arranged at different
locations to screen and melt ice prior to its arrival at other fuel
system components as is suitable for a given application.
[0028] With reference to FIG. 3, EHFS 100 is shown in plan view.
EHFS 100 includes a first heating body pair 102 and a second
heating body pair 104, each of the second heating body pair 104
being integrally coupled to each of first heating body pair 102.
First heating body pair 102 includes two adjacent heating bodies
that extend in parallel with one another along a width of EHFS 100.
In embodiments, second heating body pair 104 includes two adjacent
heating bodies that are also parallel with one another and
integrally coupled to form EHFS 100. An aperture 106 is defined
between intersecting first heating body pair 102 and second heating
body pair 104, aperture 106 extending through an axial thickness of
EHFS 100. In the illustrated embodiment first heating body pair 102
intersects second heating body pair 104 orthogonally, thereby
imparting a rectangular shape to aperture 106. As will be
appreciated, other angular relationships between first heating body
pair 102 and second heating body pair 104 are possible as is
suitable for an intended application of EHFS 100. For example,
aperture 106 can have a triangular, circular or elliptical
shape.
[0029] With reference to FIG. 4, a cross-sectional view of EHFS 100
is shown. The adjacent heating bodies of first heating body pair
102 respectively define upstream face 101 and downstream face 103
of EHFS 100. A metallic layer 120 (shown in FIG. 5) is included on
upstream facing edges of each heating body for protecting the
heating bodies from kinetic impact of ice particles (shown in FIG.
2) entrained in fluid flow F as the fluid transits aperture 106 of
EHFS 100. Upstream face 101 is configured and adapted to block ice
particles of greater size than aperture 106, fixing the particles
on the upstream side of EHFS 100 and melting ice by thermally
conducting heat into the fluid transiting the screen or ice captive
on the upstream side of EHFS 100.
[0030] As illustrated by flow arrow F, unfiltered and unheated fuel
flows downstream from conduit 16 and transits aperture 106. Ice
particles entrained in the fuel flow (shown in FIG. 2) and larger
than aperture 106 impact the metal protective layer of heating
bodies of first heating body pair 102 and second heating body pair
104 and are urged against upstream face 101 by the force of fuel
flowing across EHFS 100. Flowing fuel forces the ice particles
against EHFS 100 and abrading the ice particles against the metal
layer while heat generated by the EHFS 100 melts ice contacting
EHFS 100. Once reduced to size sufficient to transit an aperture
the fuel flow sweeps the ice particles through aperture 106 in
sizes that are less likely to damage downstream components or
impact engine operation. In embodiments, the heating bodies of
second heating body pair 104 can have a similar shape and
construction as the heating bodies of first heating body pair
102.
[0031] With reference to FIG. 5, a heating body of heating body
pair 102 is shown including a heater element 110, an insulating
layer 130, and metallic layer 120. Heater element 110 defines a
circular cross-sectional area and has a surface 112. Insulating
layer 130 defines an annular cross-sectional area, and has an inner
surface opposite surface 112 of heater element 110 and an outer
surface 132 circumferentially extending about insulating layer 130.
Metallic layer 120 defines an arcuate cross-sectional shape and has
an inner surface 122 opposing surface 132 and an exterior surface
124. Metallic layer 124 and the environment external to the heating
body are electrically insulated from heater element 110 by
insulating layer 130. Heater element 110 is thermally communicative
with the environment external to the heating body through
insulating layer 130 and metallic layer 120.
[0032] Heater element 110 is constructed from a resistive heating
material. The resistive material generates heat when an electric
current is flowed therethrough. Insulating layer 130 is constructed
from an electrically insulating material that has high thermal
conductivity, such as a ceramic material, and electrically
insulates heater element 110 from the environment external to the
heating body while efficiently conducting heat generated by the
heating body to the environment external to the heating body. In
embodiments, insulating layer 130 directly contacts heater element
110 to efficiently conduct heat from heater element 110. Metallic
layer 120 is constructed of a material resistive to impact damage
and with high thermal conductivity, and is in direct physical
contact with the underlying portion of insulating layer 130. It
thereby protects the underlying insulating layer from ice impact
damage while efficiently conducting heat generated by heater
element 110 to the environment external to heating body. Each of
insulating layer 130 and metallic layer 120 are thermally
communicative with heater element 110 and the environment external
to the heating body. In embodiments, metallic layer 120 is
constructed of a material with good thermal conductivity that
efficiently conducts heat through metal protective leading edges of
upstream face 101 of EHFS 100 and renders the EHFS 100 structurally
rigid and better adapted to resist ice impact. In embodiments,
metallic layer 120 is in direct physical contact with insulating
layer so as to efficiently conduct heat from insulating layer 130
(and underlying heater element 110) to the environment external to
the heating body, although one or more intermediate layers of
material or adhesive may be layered between the metallic layer 120,
the insulating layer 130, and the underlying heater element
110.
[0033] With reference to FIG. 6, another embodiment of a heating
body 202 is shown. Heating body 202 is similar to heating body 102,
and additionally includes an axial width Y that is greater than its
lateral width X. In embodiments, heating body 202 provides ice and
debris impact protection and efficiently conducting heat into the
environment external to heating body with reduced disturbance to
fluid flowing across heating body 202.
[0034] Embodiments of the EHFS devices described herein protect the
leading edge of the ceramic coated heating element in fuel systems
using a metallic layer disposed over the leading edges of ceramic
coated heating bodies. The metallic layer protects the underlying
ceramic layer from chipping and fracturing when impacted by ice
moving within a fluid flow transiting the EHFS. In embodiments, the
protective layer is in direct physical contact with the insulating
layer, providing good thermal conductivity between the layers.
Direct physical contact between the layers also prevents
contamination from infiltrating an interface defined by respective
surfaces of the metallic layer and the insulating layer. Limiting
the metal layer to the upstream facing edges of the heating body
also reduces any thermal conductivity penalty associated with the
metallic layer while providing impact protection for the insulating
layer. In embodiments, the metallic layer provides a streamlined
heating body contour oriented into the fluid flow, reducing the
disturbance created by the structure within the fluid flow.
Embodiments of the EHFS also provide improved reliability and
longer service life than convention EHFS devices.
[0035] The methods and systems of the present disclosure, as
described above and shown in the drawings, provide an EHFS with
superior properties including control of ice particle flow within a
gas turbine fuel system. While the apparatus and methods of the
subject disclosure have been shown and described with reference to
preferred embodiments, those skilled in the art will readily
appreciate that changes and/or modifications may be made thereto
without departing from the spirit and scope of the subject
disclosure.
* * * * *